Cooling fluid pre-swirl assembly for a gas turbine engine

ABSTRACT

A gas turbine engine includes a pre-swirl structure. Inner and outer wall structures of the pre-swirl structure define a flow passage in which swirl members are located. The swirl members include a leading edge and a circumferentially offset trailing edge. Cooling fluid exits the flow passage with a velocity component in a direction tangential to the circumferential direction, wherein a swirl ratio defined as the velocity component in the direction tangential to the circumferential direction of the cooling fluid to a velocity component of a rotating shaft in the direction tangential to the circumferential direction is greater than one as the cooling fluid exits the flow passage outlet, and the swirl ratio is about one as the cooling fluid enters at least one bore formed in a blade disc structure. An annular cavity extends between the flow passage and the at least one bore formed in the blade disc structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No. ______,(Attorney Docket No. 2010P00100US), entitled “COOLING FLUID METERINGSTRUCTURE IN A GAS TURBINE ENGINE” by Keith D. Kimmel et al., and U.S.patent application Ser. No. ______, (Attorney Docket No. 2010P00101US),entitled “PARTICLE SEPARATOR IN A GAS TURBINE ENGINE” by Todd Ebert etal., the entire disclosures of each of which are incorporated byreference herein.

FIELD OF THE INVENTION

The present invention relates to a gas turbine engine, and moreparticularly, to a gas turbine engine including a cooling fluidpre-swirl assembly that swirls cooling fluid used to cool turbine bladestructure in a turbine section of the gas turbine engine.

BACKGROUND OF THE INVENTION

In gas turbine engines, compressed air discharged from a compressorsection and fuel introduced from a source of fuel are mixed together andburned in a combustion section, creating combustion products defininghot working gases. The working gases are directed through a hot gas pathin a turbine section, where they expand to provide rotation of a turbinerotor. The turbine rotor may be linked to an electric generator, whereinthe rotation of the turbine rotor can be used to produce electricity inthe generator.

In view of high pressure ratios and high engine firing temperaturesimplemented in modern engines, certain components, such as rotatingblade structures within the turbine section, must be cooled with coolingfluid, such as compressor discharge air, to prevent overheating of thecomponents. The cooling fluid can be contaminated with various types ofparticles, which can cause blockage of turbine blade cooling holes orother structure in the turbine section that is cooled with the coolingfluid, which can shorten the life of these components.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a gasturbine engine is provided. The gas turbine engine comprises a supply ofcooling fluid, a rotatable shaft, shaft cover structure, blade discstructure coupled to the shaft having at least one bore for receivingcooling fluid, and a pre-swirl structure disposed about the shaft. Thepre-swirl structure comprises radially inner wall structure, radiallyouter wall structure spaced from the inner wall structure, and aplurality of swirl members. The inner and outer wall structures extendabout the shaft and are each coupled to the shaft cover structure. Theinner and outer wall structures define a flow passage therebetween thatincludes an inlet and an outlet and that receives fluid from the supplyof cooling fluid. The swirl members extend in the flow passage betweenthe inner and outer wall structures. Each of the swirl members includesa leading edge at the flow passage inlet and a trailing edge at the flowpassage outlet, wherein the trailing edge is offset from the leadingedge in the circumferential direction. The supply of cooling fluidsupplies cooling fluid to the pre-swirl structure such that the coolingfluid exiting the flow passage outlet has a velocity component in adirection tangential to the circumferential direction, wherein a swirlratio defined as the velocity component in the direction tangential tothe circumferential direction of the cooling fluid to a velocitycomponent of the shaft in the direction tangential to thecircumferential direction is greater than one as the cooling fluid exitsthe flow passage outlet, and the swirl ratio is about one as the coolingfluid enters the at least one bore formed in the blade disc structure.An annular cavity extends between the flow passage outlet and the atleast one bore formed in the blade disc structure.

The swirl ratio may be between about 1.15 and about 1.25 when thecooling fluid exits the pre-swirl structure.

The gas turbine engine may further comprise a particle separator thatincludes particle deflecting structure located downstream from thepre-swirl structure. The particle deflecting structure is coupled to andextends radially inwardly from the blade disc structure. The particleseparator separates solid particles from the cooling fluid after thecooling fluid exits the pre-swirl structure.

The particle separator may further comprise a particle collectionchamber upstream from the particle deflecting structure. The particlecollection chamber receives the solid particles separated from thecooling fluid.

The pre-swirl structure may remain stationary with the shaft coverstructure such that it does not rotate with the shaft during operationof the gas turbine engine, and the particle deflecting structure mayrotate with the shaft during operation of the gas turbine engine.

The annular cavity may be substantially defined by the blade discstructure, the pre-swirl structure, and the particle deflectingstructure.

The gas turbine engine may further comprise sealing structure locatedaxially between the flow passage outlet and the at least one bore formedin said blade disc structure. The sealing structure limits leakagebetween the annular cavity and a turbine rim cavity located radiallyoutwardly from said annular cavity.

The swirl members may be configured such that the cooling fluid exitingthe flow passage flows at an angle of from about 65° to about 85°relative to a central axis of the gas turbine engine.

The swirl members may be arranged such that spacing between a firstsidewall at the trailing edge of each swirl member and a second sidewallof an adjacent swirl member causes a Venturi effect as the cooling fluidflows through the flow passage, the Venturi effect resulting in apressure drop and a velocity increase of the cooling fluid flowingthrough the flow passage.

The Venturi effect may be effected by converging sidewalls of adjacentswirl members.

In accordance with a second aspect of the present invention, a gasturbine engine is provided. The gas turbine engine comprises a supply ofcooling fluid, a rotatable shaft, a non-rotatable shaft cover structuredisposed about the shaft, blade disc structure having at least one borefor receiving cooling fluid, and a pre-swirl structure disposed aboutthe shaft. The pre-swirl structure comprises radially inner wallstructure coupled to the shaft cover structure and extendingcircumferentially about the shaft; radially outer wall structure spacedfrom the inner wall structure, the outer wall structure coupled to theshaft cover structure and extending circumferentially about the shaft,the inner and outer wall structures defining a flow passagetherebetween, the flow passage including an inlet and an outlet andreceiving fluid from the supply of cooling fluid; a plurality of swirlmembers extending in the flow passage between the inner and outer wallstructures; and sealing structure located axially between the flowpassage outlet and the at least one bore formed in the blade discstructure, the sealing structure limiting leakage between the annularcavity and a turbine rim cavity located radially outwardly from theannular cavity. The swirl members each include a leading edge at theflow passage inlet and a trailing edge at the flow passage outlet andoffset from the leading edge in the circumferential direction. Thesupply of cooling fluid supplies a first portion of cooling fluid to thepre-swirl structure such that the first portion of cooling fluid exitingthe flow passage outlet has a velocity component in a directiontangential to the circumferential direction, wherein a swirl ratiodefined as the velocity component in the direction tangential to thecircumferential direction of the first portion of cooling fluid to avelocity component of the shaft in the direction tangential to thecircumferential direction is greater than one as the first portion ofcooling fluid exits the flow passage outlet. An annular cavity extendsbetween the flow passage outlet and the at least one bore formed in theblade disc structure coupled to the shaft. An axial flow distance of thefirst portion of cooling fluid within the annular cavity is greater thanabout 50 mm.

The gas turbine engine may further comprise at least one bypass passageassociated with the shaft cover structure, the at least one bypasspassage in fluid communication with the supply of cooling fluid forsupplying a second portion of cooling fluid from the supply of coolingfluid to the turbine rim cavity.

The second portion of cooling fluid flowing from the supply of coolingfluid to the turbine rim cavity may not interact with the first portionof cooling fluid.

A pressure within the annular cavity may be greater than a pressurewithin the turbine rim cavity and may also be greater than a pressurewithin a cavity located between the shaft and the shaft cover structure.

The gas turbine engine may further comprise a metering structureassociated with an outlet of each bypass passage, the metering structurecomprising at least one flow passageway formed therein for permittingthe second portion of cooling fluid in each bypass passage to pass intothe turbine rim cavity.

Each flow passageway may be formed in the metering structure at an anglesuch that the second portion of cooling fluid flowing out of each flowpassageway has a velocity component in the direction tangential to thecircumferential direction.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the present invention, it is believed that thepresent invention will be better understood from the followingdescription in conjunction with the accompanying Drawing Figures, inwhich like reference numerals identify like elements, and wherein:

FIG. 1 is a sectional view of a portion of a gas turbine engineaccording to an embodiment of the invention;

FIG. 2 is a perspective view partially in section of a portion of thegas turbine engine illustrated in FIG. 1;

FIG. 3 is a perspective view partially in section of the portion of thegas turbine engine illustrated in FIG. 2 taken from a different angle;

FIG. 4 is a cross sectional view illustrating a plurality of swirlmembers according to an embodiment of the invention;

FIG. 5 is an end view of a shaft cover structure according to anembodiment of the invention shown removed from the gas turbine engineillustrated in FIG. 1; and

FIG. 6 is a diagram illustrating swirl ratios of cooling fluid passingout of a pre-swirl structure according to an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration, and not by way oflimitation, specific preferred embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand that changes may be made without departing from the spirit and scopeof the present invention.

Referring now to FIG. 1, a portion of a gas turbine engine 10 accordingto an embodiment of the invention is shown. The engine 10 includes aconventional compressor section 11 for compressing air. The compressedair from the compressor section 11 is conveyed to a combustion section12, which produces hot combustion gases by burning fuel in the presenceof the compressed air from the compressor section 11. The combustiongases are conveyed through a plurality of transition ducts 12A to aturbine section 13 of the engine 10. The turbine section 13 comprisesalternating rows of rotating blades 14 and stationary vanes 18. A firstrow 14A of circumferentially spaced apart blades 14 coupled to a firstblade disc structure 114 and a first row 18A of circumferentially spacedapart vanes 18 coupled to an interior side of a main engine casing (notshown) and a first lower stator support structure 118 are illustrated inFIG. 1. A plurality of the blade disc structures, including the firstblade disc structure 114, are positioned adjacent to one another in anaxial direction so as to define a rotor 16. Each of the blade discstructures supports a plurality of circumferentially spaced apart bladesand each of a plurality of lower stator support structures support aplurality of circumferentially spaced apart vanes. The vanes 18 directthe combustion gases from the transition ducts 12A along a hot gas flowpath HG onto the blades 14 such that the combustion gases cause rotationof the blades 14, which in turn causes corresponding rotation of therotor 16.

As shown in FIG. 1, a shaft cover structure 20 surrounds a portion of ashaft 22, which shaft 22 is coupled to the rotor 16 for rotation withthe rotor 16. It is noted that the shaft cover structure 20 may bemounted to the main engine casing and does not rotate with the shaft 22and the rotor 16 during operation of the engine 10. In an embodiment,the shaft cover structure 20 may comprise two halves or sections thatare joined together about the shaft 22, such as, for example, bybolting, although it is understood that the shaft cover structure 20 maybe formed from additional or fewer pieces/sections. The shaft coverstructure 20 comprises a generally cylindrical member having a forwardend portion 24 and an opposed aft end portion 26.

Referring still to FIG. 1, the forward end portion 24 of the shaft coverstructure 20 includes a shaft seal assembly 28 that creates asubstantially fluid tight seal with the shaft 22. The shaft sealassembly 28 may comprise, for example, a rotating structure, such as aknife edge seal, coupled to the shaft 22, which may be in combinationwith a non-rotating seal structure, such as a honeycomb seal or anabradable material coupled to the forward end portion 24 of the shaftcover structure 20. Other suitable exemplary types of shaft sealassemblies 28 include leaf seals, brush seals, and non-contacting finseals.

The aft end portion 26 of the shaft cover structure 20 comprises apre-swirl structure 30 and defines a plurality of bypass passages 32 anda particle collection chamber 34, each of which will be described indetail herein.

An outer cover 40 is disposed radially outwardly from the shaft coverstructure 20. The outer cover 40 includes a forward end portion 42upstream and radially outward from the forward end portion 24 of theshaft cover structure 20 and an aft end portion 44 radially outward fromthe aft end portion 26 of the shaft cover structure 20. First sealstructure 46, such as, for example, a dog bone seal or diaphragm seal isdisposed between the forward end portion 24 of the shaft cover structure20 and the outer cover 40 for creating a substantially fluid tight sealtherebetween. Second seal structure 48 is located between the shaftcover structure 20 and the outer cover 40 adjacent to the respective aftend portions 26, 44 thereof. The second seal structure 48 creates asubstantially fluid tight seal between the aft end portion 26 of theshaft cover structure 20 and the aft end portion 44 of the outer cover40. In the embodiment shown, the second seal structure 48 also providesa structural support for the shaft cover structure 20 via the outercover 40. It is noted that the outer cover 40 is non-rotatable and isstructurally supported within the engine 10 by the main engine casingvia a plurality of struts (not shown).

A cooling fluid chamber 50 is located radially between the shaft coverstructure 20 and the outer cover 40 and axially between the first andsecond seal structures 46, 48. The cooling fluid chamber 50 receivescooling fluid from a supply of cooling fluid, e.g., compressor bleed airthat is cooled in an external cooler (not shown), from a plurality ofcooling fluid feed tubes 52 (one shown in FIG. 1). The cooling fluidfeed tubes 52 deliver the cooling fluid into the cooling fluid chamber50 through one or more respective apertures 54 formed in the outer cover40. The cooling fluid, which may have a temperature of, for example,between about 250-350° F., is used to cool the shaft cover structure 20,the shaft 22, and structure in the turbine section 13 of the engine 10,as will be described in greater detail herein.

Referring additionally to FIGS. 2 and 3, a first portion of coolingfluid supplied by the cooling fluid chamber 50 flows through a series ofpre-swirl passages 60 (one shown in FIGS. 1-3) that extend through theshaft cover structure aft end portion 26 from the cooling fluid chamber50 to an annular pre-swirl chamber 62. The first portion of coolingfluid flows from the pre-swirl passages 60 into the pre-swirl chamber 62and is provided to the pre-swirl structure 30.

As shown in FIGS. 2 and 3, the pre-swirl structure 30 includes aradially inner wall structure 64 that extends about the shaft 22 and isfixedly coupled to the shaft cover structure 20. The pre-swirl structure30 also includes a radially outer wall structure 66 radially spaced fromthe inner wall structure 64. The outer wall structure 66 extends aboutthe shaft 22 and is also fixedly coupled to the shaft cover structure20. The inner and outer wall structures 64, 66 define an annular flowpassage 68 therebetween, which flow passage 68 includes an inlet 70 andan outlet 72 (see also FIG. 4), through which the first portion ofcooling fluid passes after entering the pre-swirl structure 30 from thepre-swirl chamber 62.

A plurality of swirl members 74 extend in the flow passage 68 and spanbetween the inner and outer wall structures 64, 66. As more clearlyshown in FIG. 4, the swirl members 74 each include opposed first andsecond sidewalls 75A, 75B, a leading edge 76 at the flow passage inlet70 and a trailing edge 78 at the flow passage outlet 72. The leadingedge 76 of each of the swirl members 74 is offset from the trailing edge78 in the circumferential direction, as shown in FIG. 4. Thus, the firstportion of cooling fluid flowing through the flow passage 68 is causedto change direction by the swirl members 74, such that the first portionof cooling fluid exiting the flow passage outlet 72 has a velocityvector V (see FIG. 4) with a velocity component V_(TC) in a directiontangent to a circumferential direction, wherein the circumferentialdirection is defined by a first circumferential surface of the innerwall structure 64, and an axial velocity component V_(A) as it flowsdownstream toward the turbine section 13 of the engine 10, as will bedescribed in detail herein. An angle β between the velocity vector V andits velocity component V_(A) may be between about 65° and about 85°. Aradial height H (see FIG. 2) of each of the swirl members 74 accordingto an exemplary embodiment of the invention may be about 15-25 mm and achordal length L (see FIG. 4) of each of the swirl members 74 accordingto an exemplary embodiment of the invention may be about 60-105 mmaccording to one embodiment of the invention.

Referring to FIG. 4, in a preferred embodiment, the swirl members 74 areconfigured such that the cooling fluid exiting the flow passage outlet72 flows or moves in a direction D at an angle θ_(D) of from about 65°to about 85° relative to a central axis C_(A) (see FIGS. 1 and 4) of theengine 10. Such a flow direction D of the cooling fluid can be effectedby forming the trailing edges 78 of the swirl members 74 so that theyextend at an angle θ_(SM) of from about 65° to about 85° relative to thecentral axis C_(A) of the engine 10.

Further, the swirl members 74 in the preferred embodiment arecircumferentially spaced from one another so as to allow a desiredamount of cooling fluid through the flow passage 68 to adequately coolthe structure to be cooled in the turbine section 13 of the engine 10.As shown in FIG. 4, the narrowest spacing S_(P) between the trailingedge 78 of one swirl member 74 and an adjacent swirl member 74, whichspacing S_(P) may also be referred to as the throat section between theswirl members 74, is also preferably configured to obtain a desiredpressure drop, i.e., caused by a Venturi effect effected by theconverging sidewalls 75A and 75B of the swirl members 74, and to cause acorresponding velocity increase as the cooling fluid flows through theflow passage 68. According to one embodiment, the narrowest spacing Spbetween the first sidewall 75A at the trailing edge 78 of one swirlmember 74 and the second sidewall 75B of the adjacent swirl member 74may be about 10 mm, but may vary depending upon the particularconfiguration of the engine 10. It is noted that the velocity componentV_(TC) of the cooling fluid exiting the flow passage outlet 72 in thedirection tangent to the circumferential direction is preferably greaterthan a velocity component of the shaft 22 and the rotor 16 in thedirection tangent to the circumferential direction during operation ofthe engine 10, as will be discussed in greater detail herein.

Since the pre-swirl structure 30 is located close to the shaft 22, aleakage interface area between the pre-swirl structure 30 and the shaftcover structure 20 is reduced, as compared to if the pre-swirl structure30 were to be located further radially outwardly. Specifically, theleakage interface area between the pre-swirl structure 30 and the shaftcover structure 20 is defined as the area between where the radiallyinner wall structure 64 and the shaft cover structure 20 meet, inaddition to the area between where the radially outer wall structure 66and the shaft cover structure 20 come together. Since these areas arelocated generally close to the shaft 22, their circumferences arerelatively small (as compared to if these areas were located radiallyoutwardly further from the shaft 22), such that the leakage areas arerelatively small. This is compared to a configuration where the leakageareas are radially outwardly further from the shaft 22, in which casethe circumferences of the leakage interface areas would be larger. Thissame concept applies for leakage through first and second sealingstructure 98 and 106, each of which will be discussed below.

An annular cavity 84 is located downstream from the pre-swirl structure30 and extends from the flow passage outlet 72 to a plurality of bores86 formed in the first blade disc structure 114. As illustrated in FIGS.1-3, the annular cavity is substantially defined by the first blade discstructure 114, the pre-swirl structure 30, and a particle deflectingstructure 90, which particle deflecting structure 90 will be describedin detail herein. The bores 86 in the first blade disc structure 114extend radially outwardly and axially downstream through the first bladedisc structure 114 to the first row 14A of blades 14 to provide thefirst portion of cooling fluid to internal cooling circuits 14A₁ formedin the blades 14, see FIG. 1.

Referring back to FIGS. 2 and 3, a particle separator 89 according to anaspect of the present invention comprises the particle deflectingstructure 90 and the particle collection chamber 34, which, as notedabove, is defined by a portion of the shaft cover structure 20. Theparticle deflecting structure 90 is located in the annular cavity 84downstream from the pre-swirl structure 30 and upstream from the bores86 in the first blade disc structure 114. The particle deflectingstructure 90 is coupled to and extends radially inwardly from a seal arm92 of the first blade disc structure 114, and, thus, rotates with thefirst blade disc structure 114 and the rotor 16 during operation of theengine 10.

The particle deflecting structure 90 includes a radially inwardlyextending portion 94 that extends radially inwardly from the seal arm 92of the first blade disc structure 114 and a generally axially extendingportion 96. The radially inwardly extending portion 94 includes aradially inner end portion 97, which end portion 97 is curved in theradial direction such that it extends in the axial direction at its endtoward the pre-swirl structure 30 and the particle collection chamber34. The end portion 97 is located further radially inwardly than theaxially extending portion 96, which axially extending portion 96 extendsgenerally axially from the radially extending portion 94 toward thepre-swirl structure 30 and the particle collection chamber 34. However,as most clearly seen in FIG. 6, the axially extending portion 96 isslightly sloped in the radial direction as it extends toward thepre-swirl structure 30 and the particle collection chamber 34, i.e., theaxially extending portion 96 is sloped such that it expandscircumferentially in a direction toward the particle collection chamber34. As will be described in detail herein, the particle deflectingstructure 90 deflects solid particles from the first portion of coolingfluid into the particle collection chamber 34 after the first portion ofcooling fluid exits the pre-swirl structure 30.

Referring to FIGS. 2 and 3, the first sealing structure 98 is locatedradially outwardly from the annular cavity 84 between the shaft coverstructure 20 and the axially extending portion 96 of the particledeflecting structure 90. The first sealing structure 98 is locatedaxially between the flow passage outlet 72 and the bores 86 in the firstblade disc structure 114. The first sealing structure 98 limits leakagebetween the annular cavity 84 and a turbine rim cavity 100, whichturbine rim cavity 100 is defined by the first blade disc structure 114and the first lower stator support structure 118 and is locatedproximate to the hot gas flow path HG. Additional details in connectionwith the turbine rim cavity 100 will be discussed in detail herein. Thefirst sealing structure 98 may comprise, for example, one or moreknife-edge seal members 102 extending radially outwardly from theaxially extending portion 96 of the particle deflecting structure 90,and a honeycomb seal or abradable material 104 associated with the shaftcover structure 20. It is noted that other types of sealing structuremay be used.

Also shown in FIGS. 2 and 3, the second sealing structure 106 isemployed between the shaft cover structure 20 and the shaft 22 proximateto the aft end portion 26 of the shaft cover structure 20. The secondsealing structure 106 limits leakage between the annular cavity 84 and ashaft cover cavity 108, which shaft cover cavity 108 will be discussedin detail herein. The second sealing structure 106 may comprise, forexample, one or more knife-edge seal members 110 extending radiallyoutwardly from the shaft 22, and a honeycomb seal or abradable material112 associated with the shaft cover structure 20. It is noted that othertypes of sealing structure may be used.

Referring still to FIGS. 2 and 3, the shaft cover structure 20 at leastpartially defines the particle collection chamber 34, as noted above.The particle collection chamber 34 extends circumferentially about theshaft 22 and is in fluid communication with the annular cavity 84. Theparticle collection chamber 34 is located upstream of the particledeflecting structure 90 and at least partially radially outwardly fromthe annular cavity 84. As will be described in detail herein, theparticle collection chamber 34 collects particles deflected from thefirst portion of cooling fluid by the particle deflecting structure 90.It is noted that some particles may flow directly into the particlecollection chamber 34, i.e., without being deflected by the particledeflecting structure 90, as a result of the particles moving radiallyoutwardly, as will be discussed herein.

Referring to FIGS. 1-3, the bypass passages 32 provide cooling fluid,including a second portion of cooling fluid from the cooling fluidchamber 50 to a metering structure 120, which metering structure 120provides the second portion of cooling fluid from the bypass passages 32into the turbine rim cavity 100.

The bypass passages 32 according to this aspect of the present inventioncomprise two types of passages. Specifically, a plurality of primarybypass passages 132 provide cooling fluid located in the shaft covercavity 108 to the metering structure 120, wherein at least a portion ofthe cooling fluid located in the shaft cover cavity 108 is from thecooling fluid chamber 50. Further, a plurality of secondary bypasspassages 134 provide cooling fluid located in the cooling fluid chamber50 directly to the metering structure 120.

As noted above, at least a portion of the cooling fluid in the shaftcover cavity 108 that flows to the metering structure 120 through theprimary bypass passages 132 comprises cooling fluid from the coolingfluid cavity 50. Specifically, cooling fluid flows from the coolingfluid cavity 50 through one or more cooling fluid ports 136 (see FIG. 1)formed in the forward end portion 24 of the shaft cover structure 20. Aportion of this cooling fluid leaks through the shaft seal assembly 28into the shaft cover cavity 108, and then flows to the meteringstructure 120 via the primary bypass passages 132.

Additional cooling fluid in the shaft cover cavity 108 may enter theshaft cover cavity 108 from the annular cavity 84 by leaking through thesecond sealing structure 106. It is noted that cooling fluid preferablydoes not leak from the shaft cover cavity 108 into the annular cavity84, as the pressure of the cooling fluid in the annular cavity 84 ispreferably as high as or higher than the pressure of the cooling fluidlocated within the shaft cover cavity 108.

The primary bypass passages 132 in the embodiment shown extend radiallyoutwardly and axially downstream from where they communicate with theshaft cover cavity 108 to a location L_(P) (see FIG. 2) and then extendgenerally axially downstream to the metering structure 120. The radiallyand axially extending sections of the primary bypass passages 132 do notcommunicate with the pre-swirl passages 60, such that the cooling fluidin the primary bypass passages 132 does not interact with the firstportion of cooling fluid flowing through the pre-swirl passages 60 tothe pre-swirl structure 30. This is accomplished in the embodiment shownby forming the primary bypass passages 132 through the shaft coverstructure 20 at different circumferential locations than the pre-swirlpassages 60.

The secondary bypass passages 134 extend generally axially downstreamfrom the cooling fluid chamber 50 to the metering structure 120, asshown in FIGS. 2 and 3. The secondary bypass passages 134 do notcommunicate with the pre-swirl passages 60, such that the cooling fluidin the secondary bypass passages 134 does not interact with the firstportion of cooling fluid flowing in the pre-swirl passages 60 to thepre-swirl structure 30. This is accomplished in the embodiment shown byforming the secondary bypass passages 134 through the shaft coverstructure 20 at different circumferential locations than the pre-swirlpassages 60. It is noted that the secondary bypass passages 134 are alsoformed through the shaft cover structure 20 at different circumferentiallocations than the primary bypass passages 132, such that the coolingfluid flowing in the secondary bypass passages 134 does not interactwith the cooling fluid flowing in the primary bypass passages 132.

According to an aspect of the invention, the ratio of primary bypasspassages 132 to secondary bypass passages 134 may be, for example, about3 to 1. According to the embodiment shown, the number of primary bypasspassages 132 is 18 and the number of secondary bypass passages 134 is 6.

The metering structure 120 according to the embodiment shown comprises aring-shaped metering member, shown in FIG. 5, which extendscircumferentially about the shaft 22 and is received in a correspondingcircumferentially extending slot 138 formed in the aft end portion 26 ofthe shaft cover structure 20, see FIGS. 2 and 3.

As shown in FIG. 5, the metering structure 120 comprises a plurality offirst and second flow passageways 140 and 142 formed therein. The flowpassageways 140 and 142 extend through the metering structure 120 andprovide fluid communication between the bypass passages 32 and theturbine rim cavity 100. Specifically, the first flow passageways 140provide fluid communication between outlets 132A of the primary bypasspassages 132 (see FIGS. 2, 3, and 5) and the turbine rim cavity 100,while the second flow passageways 142 provide fluid communicationbetween outlets 134A of the secondary bypass passages 134 (see FIGS. 2,3, and 5) and the turbine rim cavity 100. As shown in FIG. 5, the numberof first flow passageways 140 to the number of second flow passageways142 in the embodiment shown correspond to the number of primary bypasspassages 132 and secondary bypass passages 134, i.e., 18 first flowpassageways 140 and 6 second flow passageways 142 are provided in themetering structure 120 in the embodiment shown. However, it is notedthat extra bypass passages 32, i.e., primary and/or secondary bypasspassages 132, 134, may be formed in the shaft cover structure 20 in caseit is desirable to subsequently form additional flow passageways 140and/or 142 in the metering structure 120. This may be desirable for asituation where additional cooling fluid flow into the turbine rimcavity 100 is sought. If this is the case, additional flow passageways140 and/or 142 could be formed in the metering structure 120 at thelocations of the previously blocked outlets 132A, 134A of the respectivebypass passages 132, 134 to allow additional cooling fluid to flowthrough those bypass passages 132, 134 and corresponding flowpassageways 140, 142 into the turbine rim cavity 100.

Each flow passageway 140, 142 is formed in the metering structure 120 atan angle relative to the central axis C_(A) of the engine 10, such thatcooling fluid flowing out of each flow passageway 140, 142 has avelocity component in the direction tangential to the circumferentialdirection. According to the preferred embodiment, each flow passageway140, 142 is formed at an angle of at least about 70° relative to thecentral axis C_(A) of the engine 10.

Further, each flow passageway 140, 142 has a diameter D_(FP) (see FIG.5) that is no larger than about half the size of a diameter D_(BP) (seeFIG. 2) of a corresponding one of the bypass passages 132, 134. Thus, ifit is desirable to increase the amount of cooling fluid that passesthrough the metering structure 120 from the bypass passages 32 into theturbine rim cavity 100, the diameters D_(FP) of select ones or all ofthe flow passageways 140, 142 can be increased to accommodate theincreased flow volume. Alternatively, if it is desirable to decrease theamount of cooling fluid that passes through the metering structure 120from the bypass passages 32 into the turbine rim cavity 100, one or moreof the passageways 140, 142 could be blocked such that cooling fluiddoes not enter the turbine rim cavity 100 through the blockedpassageways 140, 142.

Since the diameters D_(BP) of the bypass passages 32 are larger than thediameters D_(FP) of the flow passageways 140, 142, the bypass passages32 can accommodate the additional flow volume without being altered. Itis noted that the diameters D_(BP) of the bypass passages 32 and thediameters D_(FP) of the flow passageways 140, 142 are sized so as toprovide a sufficient amount of cooling fluid into the turbine rim cavity100 from the flow passageways 140, 142 to adequately cool the firstblade disc structure 114 and the first lower stator support structure118 and to reduce or prevent hot combustion gas ingestion into theturbine rim cavity 100 from the hot gas flow path HG. That is, asufficient amount of cooling fluid is provided into the turbine rimcavity 100 to maintain the pressure within the turbine rim cavity 100 ata level wherein leakage of hot combustion gases from the hot gas flowpath HG into the turbine rim cavity 100 is substantially prevented.However, in the preferred embodiment, the diameters D_(BP) of the bypasspassages 32 and the diameters D_(FP) of the flow passageways 140, 142are sized so as to limit the amount of cooling fluid provided to theturbine rim cavity 100; hence, maintaining the pressure within theturbine rim cavity 100 below the pressure within the annular cavity 84and not providing more cooling fluid into the turbine rim cavity 100than is needed. Thus, any leakage between the turbine rim cavity 100 andthe annular cavity 84 through the first sealing structure 98 is from theannular cavity 84 into the turbine rim cavity 100. This is preferable,as cooling fluid leaking from the turbine rim cavity 100 into theannular cavity 84 could reduce the velocity component V_(TC) of thefirst portion of cooling fluid flowing into the bores 86 in the firstblade disc structure 114, which is undesirable.

During operation of the engine 10, compressed air from the compressorsection 11 is provided to the combustion section 12 and is burned withfuel to create hot working gases as discussed above. The hot workinggases from the combustion section 12 are directed into and through thetransition ducts 12A and are released into the turbine section 13. Theworking gases flow through the hot gas path HG in the turbine section 13where the working gases are expanded and cause the blades 14 and bladedisc structures to rotate to effect rotation of the rotor 16 and theshaft 22.

Cooling fluid, e.g., compressor bleed air that may be cooled in anexternal cooler, enters the cooling fluid chamber 50 via the coolingfluid feed tubes 52, see FIG. 1. A first portion of the cooling fluidflows to the pre-swirl structure 30 through the pre-swirl passages 60,wherein the first portion of cooling fluid flows through the flowpassage 68 of the pre-swirl structure 30.

As the first portion of cooling fluid passes through the flow passage 68of the pre-swirl structure 30, the swirl members 74 provide to thecooling fluid a velocity component V_(TC) in the direction tangential tothe circumferential direction, as discussed above. This tangentialvelocity component V_(TC) of the first portion of cooling fluid as thefirst portion of cooling fluid exits the flow passage outlet 72 is suchthat a swirl ratio, which is defined as the velocity component V_(TC) ofthe cooling fluid in the direction tangential to the circumferentialdirection to a velocity component of the shaft 22 in the directiontangential to the circumferential direction, is greater than one. In apreferred embodiment for the engine 10 illustrated herein, as thecooling fluid passes out of the pre-swirl structure 30, the swirl ratiois preferably between about 1.15 and about 1.25. It is noted that thedesired swirl ratio of the cooling fluid passing out of the pre-swirlstructure 30 may vary depending on the particular engine in which thepre-swirl structure 30 is employed. For example, for some types ofengines, this swirl ratio may be as high as about 3. In FIG. 6, swirlratios of the cooling fluid at relevant sections of the engine 10 areillustrated.

The cooling fluid passing out of the pre-swirl structure 30 enters theannular cavity 84, where the first portion of cooling fluid flowscircumferentially, i.e., due to passing through the pre-swirl structure30, and also flows axially downstream toward the bores 86 formed in thefirst blade disc structure 114. It is noted that the downstream flow ofthe cooling fluid is caused by the pressure in the internal coolingcircuits 14A₁ formed in the blades 14 being lower than both the pressureof the cooling fluid in the cooling fluid chamber 50 and the pressure ofthe cooling fluid in the annular cavity 84.

The axial flow of the first portion of cooling fluid through the annularcavity 84 is desirable to allow for particles to flow to the radiallyouter portion of the annular cavity 84, such that the particles can beremoved from the first portion of cooling fluid by the particleseparator 89. Specifically, as the first portion of cooling fluid flowscircumferentially in the annular cavity 84, solid particles, such asrust particles, sand, etc., which may be carried with the first portionof cooling fluid, flow radially outwardly to the radially outer portionof the annular cavity 84. This radially outer flow of the solidparticles is caused by centrifugal forces that act on the particles,which have more mass and therefore more momentum than the cooling fluidwith which the particles are flowing.

Since the solid particles are caused to flow to the radially outerportion of the annular cavity 84, some of the particles flow directlyinto the particle collection chamber 34. Other particles flow axiallythrough the annular cavity 84 and contact the radially inwardlyextending portion 94 of the particle deflecting structure 90. Uponcontacting the radially inwardly extending portion 94 of the particledeflecting structure 90, the particles are deflected thereby and flowaxially upstream along the slight radial slope of the axially extendingportion 96 of the particle deflecting structure 90 toward the particlecollection chamber 34. It is noted that the tendency for the particlesto flow upstream may be caused, at least in part, by the slight radialslope of the axially extending portion 96 and the centrifugal forcesacting on the particles that cause the particles to flow radiallyoutwardly, i.e., caused by their mass.

The majority of the solid particles deflected by the particle deflectingstructure 90 are collected in the particle collection chamber 34, wherethey can be removed therefrom, for example, during maintenance of theengine 10. However, it is noted that a small amount of the particles mayflow through the first sealing structure 98 into the turbine rim cavity100. It is believed that these particles may eventually pass into thehot gas flow path HG, where they may be burned off by the hot combustiongases or carried along the hot gas path HG with the combustion gases. Itis also noted that some small particles may not have enough mass to flowto the radially outer portion of the annular cavity 84. These smallparticles may flow with the cooling fluid into the bores 86 in the firstblade disc structure 114. However, most of the larger particles arebelieved to be separated and removed from the cooling fluid by theparticle separator 89.

It is noted that an axial flow distance A_(F) (see FIG. 6) of the firstportion of cooling fluid within the annular cavity 84 in the engine 10illustrated herein is greater than a radial flow distance R_(F) (seeFIG. 6) of the first portion of cooling fluid within the annular cavity84 as the first portion of cooling fluid flows from the flow passageoutlet 72 to the bores 86 formed in the first blade disc structure 114.In the engine 10 illustrated herein, the radial flow distance R_(F) ofthe first portion of cooling fluid within the annular cavity 84 is about⅔ of the axial flow distance A_(F) of the first portion of cooling fluidwithin the annular cavity 84, e.g., the axial flow distance A_(F) may beabout 97 mm, and the radial flow distance R_(F) may be about 62 mm.According to one embodiment, the axial flow distance A_(F) may be atleast about 50 mm, which distance is believed to allow for most of thesolid particles to be removed from the first portion of the coolingfluid by the particle separator 89. Specifically, since the particledeflecting structure 90 is located axially close to the bores 86, thefirst portion of cooling fluid swirls a sufficient amount in the annularcavity 84 to cause the majority of the solid particles to move to theradially outer portion of the annular cavity 84, such that the particlescan be separated from the first portion of the cooling fluid by theparticle separator 89, as discussed above. According to anotherembodiment, the axial flow distance A_(F) may be at least about 75 mm,such that more of the particles can be removed from the first portion ofcooling fluid.

As shown in FIG. 6, once the first portion of cooling fluid traversesthe axial flow distance A_(F) of the annular cavity 84 and solidparticles are removed by the particle separator 89, the cooling fluidflows into a free vortex portion 84A of the annular cavity 84, where thecooling fluid flows radially outwardly in the free vortex portion 84Atowards the bores 86 in the first blade disc structure 114. As the firstportion of cooling fluid flows radially outwardly into the bores 86, thevelocity component V_(TC) of the cooling fluid in the directiontangential to the circumferential direction decreases, due to a freevortex or inviscid behavior, such that the velocity component V_(TC) ofthe cooling fluid preferably becomes approximately equal to that of theshaft 22 and the rotor 16. That is, the swirl ratio just before thecooling fluid enters the bores 86 is about 1 (see FIG. 6). Thisreduction in the velocity component V_(TC) is caused by free vortexbehavior as a result of the angular momentum of the first portion ofcooling fluid dominating the angular momentum of the rotor drag in anear inviscid fashion. In this area, i.e., in the free vortex portion84A of the annular cavity 84, angular momentum of the rotor 16 isconstant.

The velocity component V_(TC) decrease of the first portion of coolingfluid causes a corresponding static pressure increase of the coolingfluid, which is obtained free of any transfer or work, i.e., of therotor 16 on the first portion of cooling fluid, and is non parasitic.The pressure of the cooling fluid is preferably increased to a pressurethat is greater than the pressure of the hot combustion gases flowingthrough the hot gas flow path HG due to both a free vortex staticpressure increase resulting from the decrease in the velocity componentV_(TC) and a forced vortex total pressure increase in the bores 86resulting from the rotation of the bores 86. Hence, hot gas ingestioninto the internal cooling circuits 14A₁ formed in the blades 14 issubstantially avoided. It is noted that it may be desirable for thepressure of the cooling fluid as it enters the bores 86 in the firstblade disc structure 114 to be equal to a preset value defined by theengine manufacturer for a given engine to ensure that the pressure ofthe cooling fluid entering the bores 86 is slightly greater than thepressure of the hot combustion gases flowing through the hot gas flowpath HG.

It is noted that, since the bores 86 extend radially outwardly as thecooling fluid passes therethrough, the cooling fluid is caused to moveat the same rotational speed as the first blade disc structure 114,i.e., such that the swirl ratio is equal to 1 as the cooling fluid flowswithin the bores 86. Since the first portion of cooling fluid and thefirst blade disc structure 114 include generally the same velocitycomponent in the direction tangential to the circumferential directionjust prior to the cooling fluid entering the bores 86, i.e. the swirlration is about 1 just prior to the cooling fluid entering the bores 86,the rotor 16 is not required to increase the velocity component V_(TC)of the cooling fluid up to that of the first blade disc structure 114.This is desirable, because if the velocity component V_(TC) of thecooling fluid were to be increased by the rotor 16, a correspondingpressure drop and temperature increase would result from the velocityincrease. The temperature increase would result in an increase in thetemperature of the first portion of cooling fluid flowing into the bores86. Such a temperature increase is undesirable, as it would adverselyaffect cooling of the blades 14 and the other structure to be cooledwithin the turbine section 13. Further, by decreasing or avoiding thepressure drop of the first portion of cooling fluid as it enters thebores 86, an increased pressure drop is achieved as the first portion ofcooling fluid passes through the pre-swirl structure 30. Thus, acorresponding velocity component V_(TC) increase of the cooling fluid,i.e., due to the pressure drop increase, is increased as the firstportion of cooling fluid passes through the pre-swirl structure 30.

Additionally, since the rotor 16 is not required to increase thevelocity component V_(TC) of the cooling fluid up to that of the firstblade disc structure 114 prior to the cooling fluid entering the bores86, the rotor 16 is not required to expend any work that would otherwisebe required to increase the velocity component V_(TC) of the coolingfluid up to the same velocity component as the first blade discstructure 114 as the cooling fluid enters the bores 86. Hence, workexpended to rotate the rotor/shaft is believed to be conserved, whichincreases the efficiency and output of the engine 10. Further, theconservation of the rotor work may result in an increase in the rotatingvelocity of the rotor/shaft and/or a reduction in the amount of fuelrequired to rotate the rotor/shaft. It is noted that some work must bedone by the rotor 16 to maintain the swirl ratio at 1 as the firstportion of cooling fluid flows radially outwardly in the bores 86.However, the work saved by the rotor 16 not being required to increasethe velocity component V_(TC) of the cooling fluid up to the samevelocity component as the first blade disc structure 114 as the coolingfluid enters the bores 86 results in the benefits discussed above.

It is also noted that, this conserving of rotor work is also believed toavoid an increase in the temperature of the cooling fluid that wouldotherwise be associated with the rotor 16 expending the work to increasethe velocity component V_(TC) of the cooling fluid up to the samevelocity component as the first blade disc structure 114 as the coolingfluid enters the bores 86. That is, if the rotor 16 were required toincrease the velocity component V_(TC) of the cooling fluid as thecooling fluid enters the bores 86, the work done by the rotor 16 wouldheat up the cooling fluid entering the bores 86, i.e., caused by acombination of Euler work and/or windage forces or friction forces.However, since this work of the rotor 16 to increase the velocitycomponent V_(TC) of the cooling fluid is not needed, the temperatureincrease of the cooling fluid associated with the work is avoided.Hence, the cooling fluid flowing into the cooling fluid chamber 50 neednot be as cool as in a situation where the cooling fluid would otherwisebe heated by the Euler work and/or windage forces or friction forces.

Moreover, since the majority of the solid particles in the first portionof cooling fluid are deflected by the particle deflecting structure 90and captured in the particle collection chamber 34, particle flow intothe bores 86 and into the internal cooling circuits 14A₁ formed in theblades 14 downstream from the bores 86 is reduced. Reducing the numberof particles and the sizes of the particles that enter bores 86 and theinternal cooling circuits 14A₁ formed in the blades 14 is believed toimprove cooling to the blades 14, as particles (especially largeparticles) can clog or otherwise block cooling passages and/or coolingholes that deliver the cooling fluid to the blades 14 and otherstructure to be cooled by the cooling fluid. Since these coolingpassages and/or cooling holes are not likely to be blocked by particles,i.e., since the particles are separated from the cooling fluid by theparticle separator 89, these cooling passages and/or cooling holes maybe designed to have smaller diameters that in prior art engines. This isbecause diameters of cooling passages and/or cooling holes in prior artengines are typically designed so as to tolerate particles to beconveyed therethrough along with the cooling fluid. If the coolingpassages and/or cooling holes can be designed to have smaller diameters,a lesser amount of cooling air may be supplied from the cooling fluidchamber 50 while still providing adequate cooling to the components tobe cooled in the turbine section 13.

A second portion of cooling fluid flows through the bypass passages 32to the metering structure 120, which conveys the second portion ofcooling fluid into the turbine rim cavity 100. As discussed above, someof the second portion of cooling fluid passes to the metering structure120 through the primary bypass passages 132, and some of the secondportion of cooling fluid flows to the metering structure 120 through thesecondary bypass passages 134. As noted above, the second portion ofcooling fluid flowing to the metering structure 120 does not interactwith the first portion of cooling fluid flowing through the pre-swirlpassages 60 to the pre-swirl structure 30.

Since the flow passageways 140, 142 formed in the metering structure 120are angled relative to horizontal, the second portion of cooling fluidflowing into the turbine rim cavity 100 from the metering structure 120includes a velocity component in the direction tangential to thecircumferential direction in the same direction as the rotor 16 and theshaft 22 rotate. Thus, the second portion of cooling fluid entering theturbine rim cavity 100 from the metering structure 120 does not slowdown the rotor 16, i.e., due to windage forces, which is believed tofurther increase the efficiency of the engine 10.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A gas turbine engine comprising: a supply of cooling fluid; arotatable shaft; shaft cover structure; blade disc structure coupled tosaid shaft having at least one bore for receiving cooling fluid; apre-swirl structure disposed about said shaft, said pre-swirl structurecomprising: radially inner wall structure coupled to said shaft coverstructure, said inner wall structure extending about said shaft;radially outer wall structure spaced from said inner wall structure,said outer wall structure coupled to said shaft cover structure andextending about said shaft, said inner and outer wall structuresdefining a flow passage therebetween, said flow passage including aninlet and an outlet and receiving fluid from said supply of coolingfluid; and a plurality of swirl members extending in said flow passagebetween said inner and outer wall structures, said swirl members eachincluding a leading edge at said flow passage inlet and a trailing edgeat said flow passage outlet and offset from said leading edge in thecircumferential direction; wherein said supply of cooling fluid suppliescooling fluid to said pre-swirl structure such that the cooling fluidexiting said flow passage outlet has a velocity component in a directiontangential to the circumferential direction; wherein a swirl ratiodefined as the velocity component in the direction tangential to thecircumferential direction of the cooling fluid to a velocity componentof said shaft in the direction tangential to the circumferentialdirection is greater than one as the cooling fluid exits said flowpassage outlet and the swirl ratio is about one as the cooling fluidenters said at least one bore formed in said blade disc structure; andwherein an annular cavity extends between said flow passage outlet andsaid at least one bore formed in said blade disc structure.
 2. The gasturbine engine according to claim 1, wherein the swirl ratio is betweenabout 1.15 and about 1.25 when the cooling fluid exits said pre-swirlstructure.
 3. The gas turbine engine according to claim 1, furthercomprising a particle separator including particle deflecting structurelocated downstream from said pre-swirl structure, said particledeflecting structure coupled to and extending radially inwardly fromsaid blade disc structure, wherein said particle separator separatessolid particles from the cooling fluid after the cooling fluid exitssaid pre-swirl structure.
 4. The gas turbine engine according to claim3, wherein said particle separator further comprises a particlecollection chamber upstream from said particle deflecting structure,said particle collection chamber receiving the solid particles separatedfrom the cooling fluid.
 5. The gas turbine engine according to claim 3,wherein said pre-swirl structure remains stationary with said shaftcover structure and does not rotate with said shaft during operation ofthe gas turbine engine, and said particle deflecting structure rotateswith said shaft during operation of the gas turbine engine.
 6. The gasturbine engine according to claim 3, wherein said annular cavity issubstantially defined by said blade disc structure, said pre-swirlstructure, and said particle deflecting structure.
 7. The gas turbineengine according to claim 1, further comprising sealing structurelocated axially between said flow passage outlet and said at least onebore formed in said blade disc structure, said sealing structure limitsleakage between said annular cavity and a turbine rim cavity locatedradially outwardly from said annular cavity.
 8. The gas turbine engineaccording to claim 1, wherein said swirl members are configured suchthat the cooling fluid exiting said flow passage flows at an angle offrom about 65° to about 85° relative to a central axis of the gasturbine engine.
 9. The gas turbine engine according to claim 1, whereinsaid swirl members are arranged such that spacing between a firstsidewall at said trailing edge of each said swirl member and a secondsidewall of an adjacent swirl member causes a Venturi effect as thecooling fluid flows through said flow passage, the Venturi effectresulting in a pressure drop and a velocity increase of the coolingfluid flowing through said flow passage.
 10. The gas turbine engineaccording to claim 9, wherein the Venturi effect is effected byconverging sidewalls of adjacent swirl members.
 11. A gas turbine enginecomprising: a supply of cooling fluid; a rotatable shaft; anon-rotatable shaft cover structure disposed about said shaft; bladedisc structure having at least one bore for receiving cooling fluid; apre-swirl structure disposed about said shaft, said pre-swirl structurecomprising: radially inner wall structure coupled to said shaft coverstructure and extending circumferentially about said shaft; radiallyouter wall structure spaced from said inner wall structure, said outerwall structure coupled to said shaft cover structure and extendingcircumferentially about said shaft, said inner and outer wall structuresdefining a flow passage therebetween, said flow passage including aninlet and an outlet and receiving fluid from said supply of coolingfluid; and a plurality of swirl members extending in said flow passagebetween said inner and outer wall structures, said swirl members eachincluding a leading edge at said flow passage inlet and a trailing edgeat said flow passage outlet and offset from said leading edge in thecircumferential direction; sealing structure located axially betweensaid flow passage outlet and said at least one bore formed in said bladedisc structure, said sealing structure limits leakage between saidannular cavity and a turbine rim cavity located radially outwardly fromsaid annular cavity; wherein said supply of cooling fluid supplies afirst portion of cooling fluid to said pre-swirl structure such that thefirst portion of cooling fluid exiting said flow passage outlet has avelocity component in a direction tangential to the circumferentialdirection; wherein a swirl ratio defined as the velocity component inthe direction tangential to the circumferential direction of the firstportion of cooling fluid to a velocity component of said shaft in thedirection tangential to the circumferential direction is greater thanone as the first portion of cooling fluid exits said flow passageoutlet; and wherein an annular cavity extends between said flow passageoutlet and said at least one bore formed in said blade disc structurecoupled to said shaft, wherein an axial flow distance of the firstportion of cooling fluid within said annular cavity is at least about 50mm.
 12. The gas turbine engine according to claim 11, further comprisingat least one bypass passage associated with said shaft cover structure,said at least one bypass passage in fluid communication with said supplyof cooling fluid for supplying a second portion of cooling fluid fromsaid supply of cooling fluid to the turbine rim cavity.
 13. The gasturbine engine according to claim 12, wherein the second portion ofcooling fluid flowing from said supply of cooling fluid to the turbinerim cavity does not interact with the first portion of cooling fluid.14. The gas turbine engine according to claim 13, wherein a pressurewithin said annular cavity is greater than a pressure within the turbinerim cavity and is greater than a pressure within a cavity locatedbetween said shaft and said shaft cover structure.
 15. The gas turbineengine according to claim 12, further comprising a metering structureassociated with an outlet of each said bypass passage, said meteringstructure comprising at least one flow passageway formed therein forpermitting the second portion of cooling fluid in each said bypasspassage to pass into the turbine rim cavity.
 16. The gas turbine engineaccording to claim 15, wherein each said flow passageway is formed insaid metering structure at an angle such that the second portion ofcooling fluid flowing out of each said flow passageway has a velocitycomponent in the direction tangential to the circumferential direction.17. The gas turbine engine according to claim 11, wherein said annularcavity is substantially defined by said blade disc structure, said shaftcover structure, and said pre-swirl structure.
 18. The gas turbineengine according to claim 11, further comprising a particle separatorcomprising: particle deflecting structure located downstream from saidpre-swirl structure, said particle deflecting structure coupled to andextending radially inwardly from said blade disc structure, wherein saidparticle deflecting structure separates solid particles from the firstportion of cooling fluid after the first portion of cooling fluid passesout of said pre-swirl structure; and a particle collection chamberupstream from said particle deflecting structure, said particlecollection chamber defined at least in part by a portion of said shaftcover structure and receiving the solid particles separated from thefirst portion of cooling fluid by said particle deflecting structure.19. The gas turbine engine according to claim 11, wherein the swirlratio is about one as the cooling fluid enters said at least one boreformed in said blade disc structure.
 20. The gas turbine engineaccording to claim 1, wherein said swirl members are arranged such thatspacing between a first sidewall at said trailing edge of each saidswirl member and a second sidewall of an adjacent swirl member causes aVenturi effect as the cooling fluid flows through said flow passage, theVenturi effect resulting in a pressure drop and a velocity increase ofthe cooling fluid flowing through said flow passage, wherein the Venturieffect is effected by converging sidewalls of adjacent swirl members.